The presence of significant quantities of H.sub.2 S in various "sour" industrial gaseous streams poses a persistent problem. Although various procedures have been developed to remove and recover this contaminant, most such processes are deficient, for a variety of reasons.
In one cyclic method currently attracting attention, the sour gas is contacted with an aqueous polyvalent metal chelate or complex reactant system to produce solid sulfur which is recovered either prior to or subsequent to regeneration of the reactant. Preferred reactants are iron (III) complexes in which the iron (III) forms chelates with specified organic acids and derivatives thereof.
It has been found that the stability of some reactants employed is temperature dependent, i.e., if the temperature of the solutions is too high, some of the reactants tend to degrade or decompose. In particular, if temperatures above the melting point of sulfur are employed, some systems, such as particular iron chelate systems, tend to decompose.
On the other hand, if a solvent is employed to extract the sulfur from the solution, problems may arise if the solvent exhibits significant solubility in the solution, the gas treated, or the product sulfur. Thus, a need has existed for a gas treating system which would avoid the problems mentioned.